Many industrial processes use the application of heat to process materials. Such examples are commonly found in the semiconductor industry, wherein silicon wafers to be processed are positioned within an enclosed chamber where they are heated by some appropriate technique, such as infrared irradiation. In one form, such a semiconductor processing chamber is constructed at least partially of an optically transparent material. Lamps outside of the chamber direct energy through the transparent material onto the surface of the wafer. The wafer is heated through absorption of the thermal radiation. The heated wafer may also be treated by introducing appropriate gases into the chamber which react with the heated wafer surface.
Such processes require that the temperature of the wafer be maintained within narrow limits in order to obtain good processing results. Thus, some form of temperature monitoring technique is required. One method is to contact the wafer with a conventional thermocouple assembly, which provides wafer surface temperature feedback.
U.S. Pat. No. 5,356,486 to Sugarman, et al. discloses such a thermocouple assembly. The thermocouple assembly is used to both support the wafer and urge the thermocouple into contact with the wafer. Thermocouple assemblies such as that shown in the '486 Patent, however, do not provide sufficient degrees of freedom to allow the thermocouple to adequately contact the wafer to provide an accurate temperature feedback signal.
For example, the '486 Patent discloses several different embodiments of support structures for urging the thermocouple into contact with the underside of the wafer, each of which is fixed in position with respect to a support arm on which it is mounted. Such a construction may result in poor temperature feedback from the wafer through the thermocouple. In fact, thermocouple temperature feedback devices are sometimes rejected in favor of other temperature feedback mechanisms, such as optical pyrometry, if the thermal contact between the wafer and the thermocouple is inadequate. However, optical pyrometry does not provide adequate temperature feedback when lower temperatures are monitored. Thus, direct contact methods of temperature feedback using thermocouples continue to be favored in the low temperature regime.
Accordingly, it is an object of the present invention to provide a thermocouple assembly for use in providing temperature feedback of a surface such as a semiconductor wafer, wherein the assembly provides a thermocouple support structure that permits contact of the thermocouple with the wafer in a manner that overcomes deficiencies in the prior art.